Heretofore, there have been known two processes for preparing 1-substituted 5-acylimidazole compounds.
J. Org. Chem., 52, 2714 (1987) describes a process for preparing 5-acetyl-1-benzyl-2-methylimidazole which comprises steps of reacting 5-methylisooxazole and ammonium nitrate in trifluoroacetic acid anhydride to give 5-methyl-4-nitroisooxazole, reducing the 5-methyl-4-nitroisooxazole with aluminum amalgam to give 5-methyl-4-aminoisoxazole, subjecting the 5-methyl-4-aminoisoxazole to benzylation and acetylation to give N-benzyl-N-(5-methyl-4-isoxazole)acetamide, and reducing the N-benzyl-N-(5-methyl-4-isoxazole)acetamide. This process is industrially disadvantageous in that the process requires a large number of steps and its overall yield is such low as 28%.
J. Org. Chem., 62, 8449 (1997) describes a process for preparing a 5-formylimidazole compound which comprises reacting an amidine compound and 2-bromo-3-(1-methyl-ethoxy)-2-propenal in chloroform in the presence of potassium carbonate (yield 33-83%). This process is industrially disadvantageous because the reaction yields are variable and low, and a small amount of a structural isomer (i.e., 4-formylimidazole) is observed in addition to the desired 5-formylimidazole.